Fast detection of candida infections with a simple sensor

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What is Candida albicans?

Candida albicans is a yeast fungus that exists naturally in our body. However, if an overgrowth occurs it can lead to candidiasis, a condition that can be very dangerous for persons with compromised immune systems such as cancer, HIV positive or post-transplant patients. Fast detection is critical in these cases.

To avoid overuse of antifungal medication, which can have negative consequences in terms of resistance, much like the problem with multi-resistant bacteria making antibiotics less efficient, Candida infections must be detected before any treatment can be administered.

Furthermore, subsequent testing for fungus infections, once the treatment has been initiated, can be difficult because the anti-fungal drugs affect the measurements.

Today, the standard time to get test results for fungal infections is 48 hours or more. With a simple membrane based sensor technology developed by researchers at DTU Nanotech, a reduction to as little as 1 hour can be reality in the future. Quick test results are in particularly important for immunocompromised patients, for whom such an untreated infection can have fatal consequences.

Together with colleagues at DTU Nanotech and Rigshospitalet, Postdoc Dorota Kwasny has developed an electrochemical impedance sensor that can detect Candida albicans yeast. The sensor is not only much faster than today’s standard test, but also more accurate. The sensor is based on membrane sensor work developed in Associate Professor Winnie Svendsen’s research group at DTU Nanotech.

The vision is to develop a device that the general practitioners have in their own clinics, providing them with the opportunity to do the test themselves, and get immediate answers. Today, a blood sample is sent from the hospital to Statens Serum Institut for detection – adding transportation time to the already long incubation time needed for the sample to develop.

A common challenge, when developing devices for diagnostics involving biological samples, is the pre-processing phase. The biological sample, e.g. a blood sample, has to be prepared before the actual detection can begin. Dorota Kwasny explains that pre-processing is also very much of relevance in this case, because a relatively large blood sample is needed for detection of Candida albicans – 5 ml. Usually when working with a microfluidic system like this, only very small samples are needed to detect the specific items. However, for this specific purpose the concentration of yeast cells is so low in the blood that a larger sample is needed to be sure to catch the yeast cells. This new sensor contributes to solving this issue with the membrane acting as a filtering mechanism catching the yeast cells, thus making it possible to handle the larger amount of sample material.

Another major challenge during her work was the immobilization of antibodies on the electrodes, Dorota says. The electrodes are functionalized with anti-Candida antibodies to capture the Candida albicans yeast cells, however as the antibodies are immobilized on the solid surface, loss of biological activity can be problematic. Therefore, it is important to orientate the antibodies to get reproducible results. Further work is ongoing to optimize this functionality.

With the method validated, further work will also include different types of fungi and optimization of the pre-processing phase, before the sensor is ready for testing in a clinical setting, and hopefully one day can help patients getting treated faster for fungal infections.

DTU Nanotech

DTU Nanotech is the Department of Micro- and Nanotechnology at the Technical University of Denmark.

Within the field of micro- and nanotechnology, DTU Nanotech is committed to educating scientists and engineers, conducting research on an internationally competitive level, and transferring new technologies to the industry through joint programs.